Manual Section... (2) - page: link

NAME

SYNOPSIS

DESCRIPTION

link()
creates a new link (also known as a hard link) to an existing file.

If
newpath
exists it will
not
be overwritten.

This new name may be used exactly as the old one for any operation;
both names refer to the same file (and so have the same permissions
and ownership) and it is impossible to tell which name was the
"original".

RETURN VALUE

On success, zero is returned.
On error, -1 is returned, and
errno
is set appropriately.

ERRORS

EACCES

Write access to the directory containing
newpath
is denied, or search permission is denied for one of the directories
in the path prefix of
oldpath
or
newpath.
(See also
path_resolution(7).)

EEXIST

newpath
already exists.

EFAULT

oldpath or newpath points outside your accessible address space.

EIO

An I/O error occurred.

ELOOP

Too many symbolic links were encountered in resolving
oldpath or newpath.

EMLINK

The file referred to by
oldpath
already has the maximum number of links to it.

ENAMETOOLONG

oldpath or newpath was too long.

ENOENT

A directory component in
oldpath or newpath
does not exist or is a dangling symbolic link.

ENOMEM

Insufficient kernel memory was available.

ENOSPC

The device containing the file has no room for the new directory
entry.

ENOTDIR

A component used as a directory in
oldpath or newpath
is not, in fact, a directory.

EPERM

oldpath
is a directory.

EPERM

The file system containing
oldpath and newpath
does not support the creation of hard links.

EROFS

The file is on a read-only file system.

EXDEV

oldpath and newpath
are not on the same mounted file system.
(Linux permits a file system to be mounted at multiple points, but
link()
does not work across different mount points,
even if the same file system is mounted on both.)

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001 (but see NOTES).

NOTES

Hard links, as created by
link(),
cannot span file systems.
Use
symlink(2)
if this is required.

POSIX.1-2001 says that
link()
should dereference
oldpath
if it is a symbolic link.
However, since kernel 2.0,
Linux does not do so: if
oldpath
is a symbolic link, then
newpath
is created as a (hard) link to the same symbolic link file
(i.e.,
newpath
becomes a symbolic link to the same file that
oldpath
refers to).
Some other implementations behave in the same manner as Linux.
POSIX.1-2008 changes the specification of
link(),
making it implementation-dependent whether or not
oldpath
is dereferenced if it is a symbolic link.
For precise control over the treatment of symbolic links when
creating a link, see
linkat(2).

BUGS

On NFS file systems, the return code may be wrong in case the NFS server
performs the link creation and dies before it can say so.
Use
stat(2)
to find out if the link got created.